Field of the Disclosure
The present disclosure generally relates to a high temperature motor seal for an artificial lift system.
Description of the Related Art
Electric submersible pumping systems (ESPs) are widely used throughout the world for recovering subterranean fluids to the earth's surface. For the long term successful operation of such ESPs, the electric motor is supplied with motor oil. The motor oil not only lubricates the motor, it also cools the motor to prevent overheating. Typically, this motor oil is partially contained within a device commonly referred to as a motor seal (aka motor protector or seal section). Conventional motor seals typically include one or more elastomeric bags. These elastomeric bags serve to equalize the fluid pressure within the motor and prevent well fluids from contaminating the motor oil. Contamination of the motor oil by well fluid greatly reduces the life of the motor.
Operation of the motor heats the motor oil and as the temperature of the motor oil increases, the oil tends to expand and the pressure within the motor tends to increase. If the motor seal did not include an expandable member, such as the elastomeric motor protector bag, the internal pressure of the motor would increase dramatically. However, the motor protector bag expands and contracts to compensate for the varying liquid volume and to maintain a relatively constant pressure within the motor. Isolation between the motor oil and the well fluids and gases helps keep the motor oil clean to increase the longevity of the motor.
Elastomers are poorly suited for adverse well conditions due to low service temperature and susceptibility to infiltration by gases, such as hydrogen sulfide. One type of adverse well production is steam assisted gravity drainage (SAGD). SAGD wells are quite challenging to produce. They are known to produce at temperatures above two hundred degrees Celsius. They are typically horizontally inclined in the producing zone. The produced fluids can contain highly viscous bitumen, abrasive sand particles, high temperature water, sour or corrosive gases and steam vapor. Providing oil companies with a high volume, highly reliable form of artificial lift is greatly sought after, as these wells are quite costly to produce due to the steam injection needed to reduce the in-situ bitumen's viscosity to a pumpable level.